Hairspring assembly



Aug. 25, 1953 T. P. DOLBY 2,649,684

HAIRSPRING ASSEMBLY Filed Feb. 10, 1949 5 Sheets-Sheet 1 FIG! 2 trauuuunwnuuaaj INVENTOR. THOMAS P. DOLBY ATTORNEY INVENTOR. THOMAS P. DOLBY BYATTORNEY ENTOR. DOLBY BY T ATTORNEY Patented Aug. 25, 1953 HAIRSPRINGASSEMBLY Thomas P. Dolby, Elgin, Ill., assignor to Instrument SpringsManufacturing Company, Elgin, 111., a corporation of IllinoisApplication February 10, 1949, Serial No. 75,593

4 Claims.

My invention relates in general to an improved hair spring assembly fortime pieces and more specifically to a novel method of securing the endsection of the hair spring of a time piece to the collet.

All timing units include a balance staff with a collet or hub to whichone end of a hair spring must be secured while the other end of thespring is fastened to a rigid point. This spring is the heart of thetiming movement and must be perl iectly true and lie in a planehorizontal to the axis of the shaft.

Several methods have been practiced and proposed for securing the innerend of a hair spring to the collet. ods the spring end was secured tothe collet. by being clamped in a slot in the outer edge thereof. Suchmethods usually require leveling or truing operations due to theliability of a slight twist or variation in assembly, and suchoperations are costly and require great skill and patience.

An object of my invention, therefore, is to provide a hair springassembly which is always uni form and requires no expert craftsmen totrue the same after assembly.

A further object is to provide a novel method of securing the hairspring to the collet so as to provide the above uniformity and producethe completed assembly at much less cost of manufacture.

A feature of the invention is the provision of a method of securing ahairspring to its collet in such a manner that the spring will always beproperly centered relative to the collet and also be in the samehorizontal plane with-the collet and which plane is at right angles tothe axis of the balance shaft when the collet is mounted thereon. Inhorological terms the spring would be true in the round and in the fiatwithout further operations.

This result is accomplishedby using an assembly tool and a spiral shapedcentering form to hold the spring in its proper position and thenfilling an opening in the collet, into which the end of the spring isinserted, with a molten metal which when hardened holds the spring andcollet in true relationship.

Further details of the invention will be understood from the followingdetailed description in conjunction with the accompanying drawings inwhich:

Fig. 1 is a top view of the usual hair spring showing the form of thespirals and bends therein;

In most of these previous meth- 3 Fig. 2 is a sectional view thereoftaken on line AA of Fig. 1;

Fig. 3 is a top view of the collet;

Fig. 4 is a sectional view of the collet taken on line BB of Fig. 3;

Fig. 5 is a top view of the spiral shaped centering form lying in placeon the assembly tool;

Fig. 5a is a modified form of centering arrangement;

Fig. 6 is a top View of the collet, spring and form in place an theassembly tool;

Fig. '7 is a sectional view taken along line C'C in Fig. 6;

Fig. 8 is a top view of the hair spring assembly after removal from thetool and form.

Fig. 9 is a sectional view of the complete assembly taken along line D-Din Fig. 8;

Fig. 1c is a sectional view of the tool and form after removal of theassembly.

Referring now to Fig. 1, I have shown the hair spring and it will beseen that such springs when formed have the spiral coil arrangementshown and have a tail portion 2 bent at a particular angle to the bodyof the spring. The collet 3 is formed as shown in Figs. 3 and 4 with acenter opening 4 designed to fit tightly on the balance stafi of thetiming unit. A cup-like recess 5 is formed as shown with a thin innerwall 6 and a thin outer wall 1. There is a narrow saw slot 8 cut at anangle through the outer wall. This slot is slightly wider than thethickness of the hair spring I. Fig. 4 showsthe collet in sectionshowing the cup shaped portion which is deeper than the width of thespring.

In Fig. 5 I have shown a broken out section of the top of the assemblytool 9 with the centering form It in place thereon. The form as shown isof a spiral shape and is designed to hold the hair spring in its correctrelationshipto the collet when the tail piece 2 is inserted in the sawslot 8 and the spring laid around the form. The assembly tool 9 isbetter shown in Figures 6, 7 and 9. It consists of a heavy body portionwith a flange II and a center piece [2 having an upward projecting studl3 with a cupshaped space l4 into which the collet fits snugly with thewalls 6 and l projecting above the upper surface of tool 9 and with thebottom of cup 5 lying slightly below the upper surface of tool 9 asshown in Fig. '7.

The spiral form is now placed as shown in Figures 5, 6 and '7 around thecollet on top surface of tool 9 with the opening between points [5 andit of the centering form opposite the saw slot 8.

The hair spring is now placed as shown in Figores 6 and 7 with the innereoii adjacent the outer edge of form ill with the tail piece 2 passingthrough slot 8. In this position the piece 2 does not touch the sides ofslot 8 nor does it touch the bottom of opening 5 in the collet and thebot tom edges of all the coils of the spring lie fiat on the uppersurface of tool 9.

With the parts in this position the spring and collet are in theexactzre'lationship in which they are to be when finally fastenedtogether. At this time the tool 9 may be heated to a temperaturesufficient to melt soft solder or other like material with a low meltingpoint. The melted solder is then poured into the cup .shaped \opening ,5in

the collet to a point where it covers .the tail piece 2 of the hairspring and the tool is then cooled to harden the solder and thus rigidlybond the spring and collet together in "the proper relationship.

In Figures 8, 9 and 10 I have shown the parts after cooling. .Fig.8.is.a.top viewof the assembled spring and collet as removed from theassembly tool with the solder in-the cup .ofthe co1let 'ho1ding thespring "rigid therewith. Figure 9 is a sectional view taken alonglinesD-D of Fig. 8 showing how the solder has .the tail piece 2 ofspring i embedded therein .and the parts thus secured. Fig. .10 merelyshows again .the relationship of the centering form 10 as it lies on thetop of .tool :9 around :the .opening from which the assembled colletlhas.been withdrawn.

In Figurefia I have shown amodifiedarrangement in which a series of pinsI"! are secured in :thetop surface oftool .9 .to Iormthe spiralcenter-:ing form. The ,pinsare so arranged that they form .aspiral of the shapeexactly the same in contour as theouter surface of form LSO so that ahair spring .may .be .placed .with'its inner coil around these pins invthe .same manner as it is placed :around form I'O in Fig. 6.

It will .thus .be .seen that 'I have provided a .novel method .of.assemblingthespring and collet of a timing unit in such amanner that apredetermined relationship is insured by a simple operation and :that(the old .tedious and expensive truing operations .can .be dispensedwith. Further, although IZhave shown adetailedconstructionof partsanddescribed a certainprocess, it will .be understood that certainvariations 'in op- .erationormaterials andin the shape of theparts will.fall within (the .scopeof the invention as set forth in the appended.claims.

What is claimed is:

'1. In a hair spring assembly, a spiral hair spring, a collet having anopening 'for'assembling .ittoa balance stafija ring shapedopeninghavingthin outer and inner walls, a slot through the.

outer wall through which the inner end 'o fthe spring extends, and amassof low meltingpoint material hardenedaround the end'of said'spring insaid ring-shaped opening around said end-and 4 thereby rigidly securingsaid inner end of the spring within said slot with the coils of thespring in a predetermined proper relationship with the axis of thecollet. I

2. A hair spring assembly comprising a spiral coiled hair spring havingits inner end bent at an angle to the coils, a collet having a centeropening forassembling it on .a balancestafi of a timing .unit, anopening around the center opening, a slot extending into said opening,and a mass of low melting point material hardened within said openingaround the inner end of said spring to :hold the spring and collet inhorizontal and centered relationship.

.3. .Inahairspr'ing assembly, a collet having an opening .in the :uppersurface thereof with a slot through which the inner end of a hair springis inserted, means for holding the spring in fixed centered andhorizontal relation with the collet with said inner end spaced from theedges of the slot and the surfaces of the opening, consisting of ameltedmaterial hardened Within said opening to bond the collet andspring.

4. In a hair spring assembly for use in a timing unit, a collet having acenter opening for attaching the assembly to.a balance, staff, a ringshaped recess extending around the opening having thin inner and outerwalls, a slot extending through the outer wall of the recess, a fiatspiral hair spring having a tail piece on its inner spiral, said tailpiece inserted through the slot and into the recess, and a low meltingpoint hardened material within said recess and holding the spring andcollet rigidly in position with the end of the spring in said slot andthe spirals thereof in a predetermined position relative the collet.

THOMAS P. 'DOLBY.

References Cited in the file of this patent UNITED STATES PATENTS Number:Name Date 33,193 Hale Sept. ,3, 1861 643,472 Cowles ,F'eb. 13,1900915,762 Grivolas .Mar. 23, 1909 974,798 Jaooby -Nov. 8, 1910 1,104,700Ohlson July21, 1914 1,136,950 Freistadter Apr.:27, 1915 1,293,383 EatonFeb. 4, .1919 1,790,218 Appleby Jan..27, 1931 1,923,073 Brell Aug. :22,.1933 1,935,747 Ratta Nov..21, 1933 2,088,094 Robarge July 27, 19372,310,841 LCurtis -Feb. 9,1943 2,329,710 Fix .Sept. 21, 1943 2,332,856Kalajian Oct. 26, 1943 2,424,230 .Fawcett .July 22, 1947 2,475,772 Allen1 July 12, 1949 2,529,807 ,Marti Nov. 14, 1950 32,540,242 Brennan Feb.6, 1951

